MONOCLINIC DOUBLE SULPHATES CONTAINING AMMONIUM. 
53 
The values for the ammonium salt are intermediate between those for the 
rubidium and caesium salts. 
Molecular Optical Constants .—The next three, tables set forth these constants for 
all three salts of the cadmium group in comparative form. In recalculating the 
values for the rubidium and caesium salts the new values for the densities now 
determined by the immersion method were employed. From the tables it may be 
deduced that the specific refraction and dispersion of the ammonium salt stand out 
prominently higher than those of the rubidium and caesium salts ; the molecular 
dispersion of the ammonium salt also slightly exceeds that of caesium cadmium 
sulphate. As regards the most important molecular refraction, all the values for the 
ammonium salt, including the mean molecular refraction, are just slightly higher than 
the corresponding values for the rubidium salt. It is immaterial whether the formula 
of Lorenz or that of Gladstone and Dale is employed. 
Table of Specific Refraction and Dispersion (Lorenz). 
. 
■ 
Sulphate. 
Ifl 2 _ 2 
Specific refraction, —--- = n. 
( n 2 + 2 ) d 
Specific dispersion. 
»G - »C- 
For ray C (Ha)- 
For ray H 7 near G. 
cl. 
ft. 
7- 
cl. 
ft- 
7- 
cl. 
ft. 
7- 
AmCd . 
RbCcl . . . 
CsCd . . . 
0-1383 
0-1050 
0-0986 
0-1393 
0-1058 
0-0991 
0-1411 
0-1077 
0-1001 
0-1418 
0-1074 
0-1008 
0-1427 
0-1083 
0-1012 
0-1445 
0-1103 
0-1023 
0■0035 
0-0024 
0-0022 
0•0034 
0-0025 
0-0021 
0•0034 
0-0026 
0-0022 
Table of Molecular Refraction and Dispersion (Lorenz). 
Salt. 
Molecular refraction 
re 2 - 1 . 
M 
1 = m - 
Molecular dispersion. 
m G - m c . 
•re 2 + 2 
For ray C (Ha). 
For ray Ily near G. 
CC. 
ft. 
7- 
CL. 
ft. 
7- 
CL. 
ft. 
7- 
RbCd sulphate 
60-82 
61-32 
62-40 
62 • 22 
62-75 
63-88 
1-40 
1-43 
1-48 
AmCd ,, 
61-62 
62-05 
62-83 
63-14 
63-57 
64-35- 
1 • 52 
1-52 
1-52 
CsCd 
66-42 
66-70 
67-41 
67-89 
68-17 
68-92 
1-47 
1-47 
1-51 
